Evidence-based preventive services for the early detection of cancer and other health conditions offer profound health benefits, yet Americans receive only half of indicated services. Government and specialty society policy initiatives are promoting the adoption of information technologies to engage patients in their care, such as personal health records (PHRs), but the current functionality may not fully utilize the technology's potential. We developed a theory-driven interactive PHR that uses its higher functionality to more deeply engage patients in health promotion. The model defines five levels of PHR functionality: (1) collecting patient information, (2) integrating with electronic health records (EHRs), (3) translating information into lay language, (4) providing individualized, guideline-based clinical recommendations, and (5) facilitating patient action. We hypothesize that implementing PHRs with these higher levels of functionality will inform and activate patients in ways that simpler PHRs cannot achieve and will increase uptake of preventive services. However, realizing this vision in practice requires both technological upgrades and practice engagement. Our prior work in Virginia practices demonstrated that patients who used such a system were more up-to-date with preventive care. We now propose a 2-phase trial to evaluate whether this functionality is scalable across a large number of practices and how its uptake differs for minority and disadvantaged patients. In Phase 1 (years 2-3), we will randomize 46 practices from three practice-based research networks in eight states to implement a PHR with advanced versus simpler functionality. Control practices will use their existing PHR. Intervention practices will upgrade their PHR to feature an interactive preventive health record (IPHR) that we have previously developed and tested. Intervention practices will locally tailor the IPHR content and learn how to integrate new functions into practice. Phase 1 will feature an implementation assessment in intervention practices, based on the RE-AIM model, to measure Reach (creation of IPHR accounts by patients), Adoption (practice decision to use the IPHR), Implementation (consistency, fidelity, barriers, and facilitators of use), and Maintenance (sustained use). The randomized comparison of intervention and control practices will measure the incremental effect of the IPHR on shared decision-making and receipt of cancer screening tests compared to traditional PHRs (Effectiveness). Data sources will include the EHR/PHR/IPHR databases, patient and practice surveys, field notes, practice learning collaborative transcripts, practice diaries, and patient focus groups that oversample minorities. In Phase 2 (years 4-5), the networks will offer the IPHR to all (up to 278) non-intervention practices to observe whether the networks can implement the IPHR more broadly (Scalability). This study will inform future efforts to use patient-centered information technology to promote cancer prevention and the feasibility of national dissemination.